Projectors (projection display apparatuses) using a reflective liquid crystal display element called LCOS (Liquid Crystal On Silicon) have high resolution. Hence, in recent years, such projectors have become widespread as large-screen display apparatuses. There have been proposed optical systems using the reflective liquid crystal display element and a polarizing beam splitter (PBS) (for example, refer to PTL 1 and PTL 2).
In the optical system disclosed in PTL 1, light is separated by color into light of the three primary colors R (red), G (green), and B (blue), and light of each of the primary colors is guided to a reflective liquid crystal display element corresponding to the color. A retardation film having wavelength selectivity (a wavelength selective retardation film) is used to separate light into the three primary colors. The wavelength selective retardation film is configured to selectively rotate a polarization direction of only light in a wavelength band corresponding to one of the three primary colors, for example, a red band. Light passes through such a wavelength selective retardation film, which causes the wavelength selective retardation film to selectively rotate only a polarization direction of light in the red band to output the light in the red band having a polarization direction different by 90 degrees from polarization directions of light in a green band and light in a blue band. Thereafter, the light passes through a PBS, which makes it possible to separate the light in the red band from the light in the green band and the light in the blue band.
In the optical system disclosed in PTL 2, light of each of the three primary colors is guided to a LCOS corresponding to the color. However, in order to separate light into the three primary colors, first, a dichroic mirror separates the light into combined light of red light and blue light, and green light. Thereafter, the wavelength selective retardation film is used to rotate polarization of only blue light derived from the combined light of red light and blue light, thereby allowing the PBS to separate the combined light of red light and blue light into red light traveling toward a LCOS for red and blue light traveling toward a LCOS for blue.